# Phase 2: OECD Null Diagnosis

Does adding OECD interaction explain why Z₁ weakens in OECD samples?

| DV | Model | Z₁ | Z₁×OECD | Total (OECD) | N |
|---|---|---|---|---|---|
| ca_gdp | Baseline | 29.765** | -- | -- | 7624 |
| ca_gdp | +OECD int. | 22.457 | -52.375 | -29.918 | 7624 |
| gross_savings_gdp | Baseline | 114.147*** | -- | -- | 6642 |
| gross_savings_gdp | +OECD int. | 127.168*** | -119.086* | 8.082 | 6642 |
| gross_investment_gdp | Baseline | 32.616*** | -- | -- | 6620 |
| gross_investment_gdp | +OECD int. | 36.412*** | -7.893 | 28.519 | 6620 |
| govt_bond_10y | Baseline | -13.743 | -- | -- | 1018 |
| govt_bond_10y | +OECD int. | -6.872 | -6.872 | -13.743 | 1018 |
| nfa_gdp | Baseline | -0.966 | -- | -- | 7712 |
| nfa_gdp | +OECD int. | -2.539 | 3.964 | 1.424 | 7712 |

*If Z₁×OECD is negative and significant, OECD membership attenuates the demographic effect.*
